Shipments of Apple Inc.'s iPhones in Japan fell 10.6 percent in 2015 from the previous year to 14.73 million units, marking the first drop since they went on sale in the country in 2008, a private research company said Saturday.

The decline was attributable to sluggish sales of new iPhone 6s and iPhone 6s Plus smartphones that went on sale last fall, according to MM Research Institute Ltd.

While Apple still dominates the Japanese mobile phone market, its share was trimmed to 41.2 percent from 43.1 percent in 2014. Sony came second with a 13.9 percent market share, followed by Sharp at 11.9 percent.

Since the communications ministry is asking mobile carriers to review drastic discount policies, MM Research Institute projects iPhone's shipments and market share, which have benefited from great discounts when users switch from another carrier's smartphone, will decrease further.

While Apple saw a decline in iPhone sales, sales of smartphones powered by Android operating systems jumped 15.0 percent to 12.85 million units in 2015 from the previous year.

Overall shipments of smartphones totaled around 27.60 million units last year, down 0.4 percent from 2014. Shipments of conventional mobile phones plunged 22.6 percent to 8.19 million units in 2015, slipping below the 10 million mark for the first time since the research company started the survey in 2000.